This is just an observation, but if you mark an already marked receiver, then that would be considered re-manufacturing the receiver with whoever’s companies name that you added.
For example, if you have a "Armory" receiver and you mark it with the Zastava name, logo and address, then you're indicating to the authorities that the receiver was either (A) originally manufactured by Zastava and Armory imported the receiver in, or (B) the Receiver was made by Armory and exported/sold to Zastava, making the authorities wonder why it's still in the country.
Remember, the 4473 yellow form (now white) request information like "the manufacturer and/or import" of the weapon. So if you sold it and a dealer puts it in his book as a Zastava made gun, the authorities can come back to you for remanufacturing a gun, with a false company and they can also nail you for manufacturing a weapon without paying federal excise tax.
In the totally opposite side of the spectrum, if the rear sight tower was marked with those markings, then you're not modifying the receiver.
To be on the safe side, do what the Yugos do, mark the sight tower.
That's my two-cent worth.